Safety device for manhole covers or the like



June 18, 1929. M. H. BORLAND 1.717. 4

SAFETY DEVICE FOR MANHOLE COVERS OR THE LIKE Filed May 1927 2Sheets-Sheet l June 18, 1929. H, BORLAND 1.717.364

swan DEVICE FOR rmmom: covsa's on was LIKE Filed May 3, 1927 2Sheets-Sheet 2 @Wvmg Patented June 18, 1929.

v UNITED STATES 1,717,364 PATENT OFFICE.

MATTHEWIL BORLAND, OF EAST PROVIDENCE, RHODE ISLAND.

SAFETY DEVICE FOR MANHOLE COVERS OR THE LIKE.

Application filed May 3, 1927. Serial No. 188,586.

This invention relates to safety devices for the covers of manholes orother openings leading from underground basins, passages or conduits;for the vent openings in tanks; for hatches on ships; and for othersimilar purposes.

A principal object of the invention is to provide a cover or closure formanholes, hatchways and other openings having means for securing it inthe opening to permit it to lift therefrom, but to prevent it from beingblown oil and projected upwardly under the force of an explosion in orbelow the manhole or opening.

Another object of the invention is to provide a device of the typespecified wherein the cover or closure may be conveniently ap-' plied toits seat in the opening and removed therefrom while being locked againstaccidental release or forcible projection from the opening.

Another object of the invention is to provide a device of the typespecified in which the locking device is of simple construction andproof against derangement or getting out of order.

Further objects of the improvement are set forth in the followingspecification, which describes a preferred embodiment of the inventionas illustrated in the accompanying drawings. In the drawings:

Fig. 1 is a plan view showing the improved device with the manhole coverseated in its frame or ring;

Fig. 2 is a vertical sectional view taken on line 22 of Fig. 1 andshowingthe manhole cover in its normal seated position;

Fig. 3 is a similar view showing the man hole cover raised to vent theopening and held from release by the locking means; and

Fig. 4 is an enlarged perspective view of the cover showing the improvedlocking means on its under side.

My improved device is adapted for use with manholes or vent openingsleading from underground chambers, culverts and conduits, such, forinstance, as the conduits for electrical transmission or telephonecables; for vent openings in tank cars; for hatches in the decks ofships, or for any like purpose. In the present application I havepreferred to describe and illustrate the inven 'tion by way of exampleas employed in a manhole leading from an underground conduit.

Referring to the drawings, 2 designates an annular frame or seat-ringwhich is permanently affixed in place in the masonry 3 forming the wallsof the manhole opening 4 leading to an underground passage, chamber,culvert or conduit 5 beneath a street or highway. The seat-ring 2 ispreferably formed with an annular flange 6 embedded in the masonry andprovided with a depending cylin The annular flange 6 of the seat-ring 2is provided with a plurality of countersunk holes 12 adapted to receivethe headed ends of rods or bolts 15 which extend downwardly through thewalls of the manhole, being preferably embedded in the masonry. Thelower ends of the rods or bolts 15 project through holes in a flat ringor flange 16 and are threaded to receive suitable nuts 17. The ring orflange 16 is preferably made in sectionsof arcuate form so that it maybe entered-down through the manhole and fitted against the under side ofthe walls thereof to provide means for anchoring the ends of the bolts15 which clamp the seat-ring 2 in place. Through thisarrangement, or byany other suitable means, the seat-ring 2 is securely held in place. atthe top of the manhole to prevent it from being blown upwardlytherefrom.

The improved manhole cover 10 and its locking device are shown in detailin Fig. 4 of the drawings. The cover 10 may be of circular outline witha beveled rim 18 adapted to fit within the tapered recess 9 in the topof theframe or ring 2. The underside of the cover 10 is flat to adapt itto rest against the inserted seat-ring lland the top of the cover may beeither flat or crowned as shown in Figs. 2 and 3. Depending from thecenter of the coverlO is a reinforcing hub or boss 19 and the top of thecover has a slot or depression 20 formed therein, see Fig. 1. A pin orbolt 21 is driven through the sides of the hub 19 to extend across theslot 20 whereby to provide means for lifting or turning the cover withthe hook or like appliance.

The improved locking means for the cover may be embodied in an annularflange or skirt 25 depending from the bottom of the cover 10 surroundingits hub 19 and adapted to fit within the cylindrical flange 7 of theseat-ring 2. To reduce the weight of the cover its skirt or flange 25ispreferably made of skeleton structure and supported and braced by flatribs 26 radiating from the central hub 19- The lower circumferential rimof the flange or skirt 25 is practically continuous exceptfor slottedopenings 27 extending vertically therethrough. This rim of the flange 25is joined to the bottom of the cover 2 by angular portions 28 formed tothe same circular contour as the rim and slotted longitudinally toprovide inclined cam-grooves 30. The grooves or slots 30 extend at anangle of substantially 45 degrees to the vertical and preferably thereare three or more, spaced equidistantly around the circumference of theskirt or flange 25. The lower end of each cam-slot 30 is continued in ahorizontal slot 31 leading to one of the vertical slots or openings 27through a zigzag or tortuous course. Referring particularly to Fig. 4,as herein shown the horizontal slot 31 is interrupted on its bottom edgeby an upstanding rounded lug or abutment 32 with the upper edge of theslot curved to conform thereto. The abutment 32 forms a stop or detentadjacent the end of the slot 31 for a purpose as later explained, andpreferably a second stop 34 is provided at a point beyond the firststop. In the construction herein illustrated the passage 31 is directeddownwardly around a projection or abutment 33 on the upper edge of theslot and finally passes into the vertical slot 27 across the top of asecond upstanding abutment or stop 34.

The above-described slots in the flange or skirt 25 of the cover 2 areadapted to be engaged by three or more pins or studs 35 projectinginwardly from the flangeor skirt 7 of the seat-ring 2. When the cover 10is set in position with its skirt 25 entered into the seat-ring itslower rim will rest upon the pins or studs 35. A turning movement of thecover will bring the vertical slots 27 in its skirt or flange 25 intoregister with the pins 35, whereupon the cover will drop down slightlyuntil the upper edges of the slots 31 seat against the pins. Then byturning the cover still further in a clockwise direction the tortuousportions of the slots or grooves 31 will ride over the pins 35 while thecover rises and falls slightly to accommodate the slots to the pins,until finally the pins are engaged in the inclined camportions 30 of theslots, allowing the cover to drop'down onto its seat as shown in Fig. 2of the drawings.

The application of the cover to place it in its frame or seat-ring ismade very readily by engaging a hook or bar with the cross-pin 21 in itscentral slot 20 and turning the cover in the manner above explained.When the cover has been applied to position in this manner it cannot beaccidentally displaced or removed underthe blows of trafiic or fromother cause since the tendency will be to hold it down In order toremove the cover from the opening it must be raised with respect to itsseat-ring and this is accomplished by turning the cover manually in acontraclockwise direction. When the cover 10 is rotated to the left theengagement of the pins 35 with the inclined slots 30 will cause it torise until the pins pass through the tortuous slots 31 and into thevertical entrance-openings 27 At this point the lock ing means isreleased and the cover may be lifted out from its seat-ring. It willthus be seen that the cover may be conveniently set in place or removedfrom the manhole openinp; without manipulating any bolts, nuts or otherfastening means.

As before noted, the principal purpose of the present improvement is toprovide a safety locking device to prevent the cover from being forciblyprojected from the top of the manhole or other opening should anexplosion occur therein. Highly explosive gases are liable to collect inmanholes, conduits and other underground passages and may be detonatedfrom a spark; for instance, in case of a short circuit caused bydefective insulation on electrical cables, or from other causes. Thisdangerous condition prevails in street or highway manholes where gasmains are located adjacent cable conduits, a leak in the pipes allowingthe gas to escape and seep through the ground into the conduit ormanhole. There have been many instances of explosions in manholes incity streets and great damage and loss of life may be incurred by theblowing up of the covers. An explosion may occur at one point and becommunicated along the conduit or underground passage to cause a seriesof detonations resulting in the upheaval of a number of covers in citystreets where traffic is heaviest and the chances for destruction verygreat. Similar dangerous -conditions prevail in tank cars and on vesselsused for transporting gasoline and oil from which volatile vapors aregiven off, and also on yachts, motor boats, and other ships havinghatches communicating with compartments below deck. It is my belief thatno efficient and reliable means have heretofore been proposed to preventsuch accidental blowing off of covers or hatches, and the presentinvention provides a most practical safety device for this purpose.Should an explosion occur the cover is permitted to rise to a limitedextent to vent the opening and release the gases, but is prevented fromforcible projection into the air, the method of operation of the devicebeing as follows:

Under normal conditions the cover 10 is seated in its frame 2 with theunder side of its rim resting against the annular seat-ring 11. If anexplosion should occur in the manhole or the conduit connectingtherewith its force is directed upwardly against the bottom of thecover, thereby tending to raise it away from its seat. As the cover islifted by the force of the explosion it must be rotated as the inclinedor helical grooves or slots 30 slide over the pins and this causes acamming action, tending to resist the upward movement of the cover. Inother words, the upward movement of the cover is retarded, but,nevertheless, it is prompt enough to immediately carry its rim away fromthe seat on the ring 2 whereby a vent is formed for the escape of theexploding gases through the top of the manhole. Asthe cover slidesupwardly the vent opening is increased in area so that finally the forceof the explosion will be expended when the cover reaches its upwardlimit of movement with the pins 35 bottoming in the under side of thegrooves 31. The pins will thus bring up against the stops or abutments32 to prevent the cover from turning any further to release its lockingmeans. At this juncture, if the force of the explosion is entirelyrelieved the cover will drop back slightly with the upper straight edgesof the grooves 31 resting on the pins 35 to hold the cover in raisedposition. Should, however, the force of the explosion or the effect ofmomentum be such as to continue the rotative movement of the cover stillfurther the pins may ride up over the curved stop or abutment 32 anddown into the depression therebey'ond. It is to be understood thatordinarily the first stops 32 are sufiicient for restraining the coverfrom furthermovementso that it will be locked in raised position asshown in Fig. 3 of the drawings. That is to say, the second upstandingabntments 34: are provided as a precautionary measure to avoid anypossible chance of the cover being entirely released, it beingpractically impossible for the cover to be turned by the force of theexplosion to such an extent as to permitthe pins 35 to travel the wholelength of the tortuous passages 31 leading from the inclined slots 30 tothe vertical openings 27.

It is to be particularly noted thatwhen the cover is carried upwardly orraised with its rim above the seat in its frame it will be held in thisposition until closed manually by rotating it in a clockwise direction.This provides that should the cover be once lifted by the force of anexplosion it cannot close of itself again to confine the pent up gaseswhich are liable to be subjected to another detonation. For this reasonthe raising of any one cover in a series of manholes acts to vent theconduit to a sufficient extent to preventexplosions atother points.

It is to be observed that while my improved locking device for themanhole cover is extremely simple in construction and arrangement itnevertheless provides for most eflicient action to open and vent themanhole, conduit or other chamber without danger of the cover beingforcibly ejected or blown up wardly from the top thereof. l/Vhiledesigned for simplicity and economy in cost of manufacture the wholedevice is nevertheless strong and rugged to resist any explosive forceagainst the cover and is proof against damage or derangement of thelocking mechanism. The invention is thus most efficient and reliable forthe purpose described, being adapted to prevent damage, destruction andloss of life through explosions in manholes or street openings, intanks, on vessels and in any other locations.

While I have herein described and illustrated one preferred embodimentof the invention by way of example only, it is to be understood thatvarious modifications may be made in the structure and arrangementof theparts of the device without departing from the spirit or scope of theinvention. For instance, the grooves or slots herein shown as formed inthe skirt of the cover may be reversed in position and located in theinterior of the flanged seat-ring with the pins projecting from adepending portion of the cover. Other changes may be made in the formand construction of the device and its method of application which wouldfall within the scope and purview of the appended claims and, therefore,without limiting myself in this respect, I claim:

1. A safety device for manholes, hatch- Ways and other openingscomprising a frame, a cover adapted to seat on said frame,means betweenthe cover and frame acting to permit the cover to lift to apredetermined. extent from its seat under the force of an explosion, andmeans to lock the cover from returning to seated position on the frameafter it has once been lifted therefrom, whereby to provide a free ventfor the explosive gases.

2. A safety device for manholes, hatchways and other openings comprisinga frame,

a cover adapted to seat on the frame, means adapted to permit the coverto lift to a predetermined extent from its seat under the force of anexplosion, and means to lock the cover from further movement in eitherdirection until it is operated manually to release it from the frame orto return it to closedposition.

3. A device of the type specified comprising a seat-ring for a manholeor other open,- ing, a cover adapted to seat on said ring to close theopening, means on one of said elements having slots inclined to thevertical and extending circumferentially of the seatring into verticalopenings,. detent abutments atthe ends of the inclined slots, and pinsprojecting fromthe other element and normally engaging in the inclinedslots to permit the cover to be raised to a considerable extent underthe force of an explosion, said slots being open at their ends beyondthe abutments to permit release of the pins to allow removal of thecover when it is 1nanually rotated to slide the pins over the abutments.

4:. In a device of the type specified, the combination of a seat-ringtor manholes, hatchways or other openings, a cover adapted to seat onthe ring and provided with a de pending cylindrical flange, said flangehaving vertical openings in its lower rim leading to inclined slotsextending circumferentially of the flange, and means projecting from theinterior of the seat-ring and normally engaging in the inclined slots toadapt the cover to lift to a considerable extent under the force of anexplosion while thereafter holding it above the seat-ring, said coverbeing adapted for removal by manually rotating it to bring the engagingmeans in register with the openings in the lower rim of its flange.

5. In a device of the type specified, the combination of a seat-ring formanholes, hatchways and other openings, a cover adapted to seat on saidring and formed with a depending cylindrical flange fittcd to slidethrough the opening in the seat-ring, said flange formed with inclinedslots leading downwardly and communicating with vertical openings in thebottom rim of the flange, detent abutments interrupting the entrancesbetween the slots and openings, and projections on the interior of theseat-ring adapted to normally engage with the slots in the flange topermit the cover to lift under the force of an explosion and to cause itto be rotated slightly whereby the projections are carried beyond theends of the inclined slots to lock the cover in raised position in themanner and for the purpose substantially described.

6. In a device of the type specified, the combination of a seat-ring formanholes, hatchways and other openings, a cover adapted to seat on saidring and provided with a depending flange adapted to enter therethrough,said flange formed with vertical openings leading from its lower-riminto tortuous passages extending circumferentially thereof and connectedto inclined slots lead ing upwardly therefrom, and projections on theinterior of the seat-ring adapted to normally engage with the inclined.slots in the flange to permit the cover to lift under the force of anexplosion and to cause it to be retated slightly whereby the projectionsare engaged with the circumferential passages to prevent it from beingreleased from the seatring until it is turned manually to cause theprojections to ride through the tortuous passages.

7. In a device of the type specified, the combination of a seat-ring formanholes, hatchways and other openings, rods extending downwardly fromthe seat-ring through the walls of the manhole, means adjacent thebottom of the opening for anchoring the rods to adapt them to clamp theseat-ring in place, a cover adapted to seat on the ring and providedwith a depending flange fitted t0 the opening therein, said flangeformed with a plurality of vertical openings leading into groovesextending circumferentially of the cover with inclined cam-slots attheir ends, and project-ions on the interior of the seatring engagingsaid grooves in the manner and for the purpose substantially asdescribed.

8. In a device of the type specified, the combination of a seat'ringhaving an annular flange and a depending cylindrical portion, boltsextending downwardly from the annular flange, a sectional ring adaptedto abut the under side of the walls of a manhole or other opening toreceive the ends of the bolts on the seat-ring, means to secure the endsof said bolts to said sectional ring, a cover adapted to seat on theseat-ring and formed with a depending cylindrical skirt having inclinedslots in its sides, said slots being continued circumferentially in azig zag course and terminating in vertical openings leading through thebottom of the depending skirt of the cover, and pins projecting from theinterior of the seat-ring to adapt them to be engaged with the openingsand slots in the depending portion of the cover in the manner and forthe purpose substantially as described.

9. A safety device for manholes, hatchways and other openings comprisinga seatring, a cover adapted to seat on said ring, inclined grooves onone of said elements, projections on the other elementengaging in thegrooves to adapt the cover to lift to a predetermined eXtentunder theforce of an eX- plosion, tortuous passages at the ends of the MATTHEW H.BoRLANn.

